1. Technical Field
The present invention relates generally to methods for electronic document revision tracking and control. More particularly, the present invention relates to methods for emphasizing differences in graphical appearance between an original document and a modified document with attached annotations.
2. Related Art
Advancements in high speed data communications and computing capabilities have increased the use of remote collaboration for conducting business. While real-time collaboration using videoconferencing and the like are gaining in popularity, the vast majority of collaboration occurs over e-mail in the exchange of documents incorporating incremental modifications, comments, and the like. A local user may create an initial version of a document, and transmit the same to remotely located colleagues. These remote users may then make their own changes or add comments in the form of annotations appended to the document, and then transmit the new version back to the local user.
Such collaboration may involve the exchange of documents generated with word processing applications, desktop publishing applications, illustration/graphical image manipulation applications, Computer Aided Design (CAD) applications, and so forth. As utilized herein, the term “document” may refer to data produced by any of the aforementioned software applications. Furthermore, the term “content” may refer to data particular to the software application that generated it and stored in the document of the same. Due to the existence of many different computing platforms having a wide variety of operating systems, application programs, and processing and graphic display capabilities, however, it has been recognized by those in the art that a device-independent, resolution-independent file format was necessary to facilitate such exchange. In response to this need, the Portable Document Format (PDF), amongst other competing formats, has been developed.
The PDF standard is a combination of a number of technologies, including a simplified PostScript interpreter subsystem, a font embedding subsystem, and a storage subsystem. As those in the art will recognize, PostScript is a page description language for generating the layout and the graphics of a document. Further, per the requirements of the PDF storage subsystem, all elements of the document, including text, vector graphics, and raster (bitmap) graphics, collectively referred to herein as graphic elements, are encapsulated into a single file. The graphic elements are not encoded to a specific operating system, software application, or hardware, but are designed to be rendered in the same manner regardless of the specificities relating to the system writing or reading such data. The cross-platform capability of PDF aided in its widespread adoption, and is now a de facto document exchange standard. Currently, PDF is utilized to encode a wide variety of document types, including those composed largely of text, and those composed largely of vector and raster graphics. Due to its versatility and universality, files in the PDF format are often preferred over more particularized file formats of specific applications. As such, documents are frequently converted to the PDF format.
The exchange of documents according to the workflow described above may take place numerous times, with the content of the document evolving over time. For example, in various engineering projects utilizing CAD drawings, such as in architecture or product design, a first revision of the document may include only a basic outline or schematic. Subsequent revisions may be generated for review and approval as further features or details are added prior to construction or production. On a more extended timeline, multiple iterations of designs may be produced. In another example, an author or a graphics designer may produce an initial draft of a document, with editors and reviewers adding comments or otherwise marking the document and resubmitting it to the author or graphics designer. The changes are incorporated into a subsequent version. While in some instances the review and approval process is performed directly on the electronic document, there are many instances where a printed hard copy of the document is utilized. As such, the reviewer may annotate, comment upon, or edit the document directly on the hard copy thereof.
As mentioned briefly above, annotations may be added to a document for commenting on changes or suggesting changes. The annotations are separate objects overlaid on the content, and may take a variety of forms such as text, geometric shapes, and the like. Additional information typically accompanies the annotations, such as the date that it was added to the document, the user who added it, the visual style of the annotation, etc. CAD applications such as AutoCAD from AutoDesk of San Rafael, Calif., as well as other graphics-oriented applications such as those for handling PDF documents, include the aforementioned annotation features. One benefit of placing annotations on the document is that comments and suggested changes may be easily tracked from a tabular interface such as that provided by the Revu application from Bluebeam Software, Inc, of Pasadena, Calif.
During collaboration, it is often desirable to review earlier versions of a document and compare the same to a current version. By doing so, the evolution of the content may be better appreciated, and each change made to the content may be tracked for approval and other purposes. As such, there is a need for software tools that can rapidly and automatically identify differences between two documents. For example, where the document includes hundreds of pages but a change is made in only one or two sentences therein, it is difficult to manually search for the change within the large volume of text. Further, where an engineering drawing contains numerous details, but where only a single dimension is changed, manually identifying it is very time-consuming. Indeed, such minor changes may have been ignored completely by a reviewer, resulting in delays, production defects, and the like.
A number of document comparison techniques are known in the art. WORD from Microsoft Corp. of Redmond, Wash., includes a “track changes” function that allows multiple users to review, insert comments, edit, and supplement the content generated by the originator. Anything added or removed by subsequent users are highlighted with different colors, underlined, the text rendered with strikethroughs, and otherwise emphasize the difference within the document. As with the textual content comparison system of Word, graphical content comparison systems apply highlights and other emphases directly onto the content, or change certain attributes of the content. Therefore, the integrity of the content is affected. Furthermore, discerning one difference from another is difficult, particularly where there are a large number of differences. In the alternative, a separate listing or report of differences is generated, or the highlighting the differences directly on an output screen. Prior techniques frequently misidentified differences, and are thus deficient. For example, where a border is added but the content is not modified, the entire area of the border is identified as a difference along with the unchanged content, rendering the comparison process ineffective.
Accordingly, there is a need in the art for an improved method for highlighting graphical appearance differences between an original document and a modified document. More particularly, there is a need in the art for comparing the original document to the modified document and deriving annotations for appending thereto, such that the changes are quickly and easily identified.